400 million years of faithfulness – how the transcriptional regulators LEUNIG and SEUSS co-evolved to become key factors of reproductive development in Arabidopsis thaliana

During land plant evolution whole genome duplications (WGDs) occurred rather frequently, allowing gene networks governing developmental processes to expand and rewire. This may have contributed to the generation of novel expression patterns for “old” genes and tight regulation of novel genes. These molecular evolutionary processes are thought to be a prerequisite for the origin of novel traits. Land plant sexual reproduction provides many examples to learn about the molecular origin of novelties, such as the evolutionary innovations of seed plant ovules or angiosperm carpels. Within the Research Unit ICIPS, we propose to analyze the molecular evolution of a pair of transcriptional corepressors LEUNIG (LUG) and SEUSS (SEU), which both play a major role in several aspects of flower development. Interestingly they were present already before the advent of land plants and possibly acted already as repressors of transcription. Using the widely divergent ICIPS species, we aim to shed light on the general questions on how repressors evolve when many opportunities for gene network rewiring exist in diverse plant lineages that underwent independent WGDs. More specifically, we ask questions regarding the number and expression of LUG and SEU homologs in mosses, liverworts, ferns, and seed plants, and we analyze the protein interactions of the respective proteins. Moreover, we will identify their function in sexual reproduction in non-seed plants. Using these approaches, we will address the question as to how these corepressors coevolved and were recruited to transcriptionally regulate sexual reproductive organ development flowering plants such as Arabidopsis thaliana. In addition, and together with the lab of Günter Theißen (Group P5), we propose to establish the fern Ceratopteris richardii (C-fern) as a genetic model system by generating transcriptome data relevant to characterize defined stages of development and by devising a gene editing system for C-fern.